Perhaps you know scabiosas, or pincushion flowers, for their cheerful summer blooms atop tall, wiry stems. One in particular, blue Scabiosa caucasica, is widely grown and much appreciated for its cut flowers. But two of my favorites are S. columbaria 'Butterfly Blue' and S. c. 'Pink Mist'. Alan Summers, president of Carroll Gardens, a mail-order and retail nursery in Westminster, Maryland, says that these are the only perennials to bloom year-round in his zone 6 garden. "These are the best scabiosas for garden show," he notes. "They're definitely the 'bloomingist' perennials there ever were."
In contrast to other scabiosas, 'Butterfly Blue' and 'Pink Mist' tolerate regions with hot, humid summers. Summer days reach 100°F and higher in Wayside's gardens, but the plants don't seem fazed. As with all scabiosas, they require a light, well-drained soil. Given a sunny spot and consistent water, they're easy to grow (in zones 3 through 10), and they are pest and disease resistant. Just clip faded flowers to encourage more blooms. And, if you choose to shear the plants, don't cut deeply into the foliage.
'Butterfly Blue' and 'Pink Mist' look very similar except for the colors of their two-inch blooms: 'Butterfly Blue' is lilac blue and 'Pink Mist' is lilac pink. Foliage on these dwarf plants forms a lovely rich green mound that's six to eight inches high and 18 inches or more across. Strong, six- to 12-inch flower stems carry the lacy blooms above the foliage.
The duo looks great planted side by side in groups of three or more. For a mass display, space plants about 15 inches. Or, plant in small groups near the front of your mixed border.
In her southern California garden, horticulturist Cristin Fusano has created an alluring combination of colors and textures by edging 'Butterfly Blue' with pink cranesbill (Erodium reichardii) and silver thyme (Thymus vulgaris 'Argenteus'). To the side, she plants bearded iris in groups of three and five, and billowing behind is sea lavender (Limonium perezii), with airy, rich blue flower clusters.
Other scabiosa species also offer a long season of bloom. Plant them in groups of at least three for strongest visual impact. They combine comfortably in mixed borders and beds.
Plant these scabiosas in full sun in northern and coastal gardens; provide afternoon shade in the South. In addition to a well-drained soil, they prefer a neutral to alkaline pH. If your soil is acid, consider adding lime before planting. Deadhead for maximum bloom.
Scabiosa caucasica (zones 3 to 10) is the most widely grown perennial scabiosa. It thrives in areas where summers are cool and humid, such as the Pacific Northwest, and provides excellent cut flowers.
The plant spreads two feet or more, with flower stalks reaching to 2 1/2 or more feet high. The flat, lacy, two- to three-inch flower heads bloom from June through September. They're typically blue and complement the yellows of summer-blooming perennials nicely. Plants are wispy, lending a soft, airy look to the landscape.
The variety 'Fama', with its unusually large and deep blue ray flowers surrounding the central disc, is most striking. According to Alan Summers, "It's the best colored of all scabiosas." Other varieties include 'House's Hybrids', in pastel colors from soft lavender to pure white, and 'Perfecta Alba' with pure white blossoms.
S. farinosa is available locally on the West Coast. Hardy to 15°F, this rounded semishrub looks quite different from other scabiosas. It grows one to two feet tall with dark, shiny, undivided leaves and small lavender flower clusters.
S. lucida (zones 5 to is a miniature species useful in rock and naturalized gardens. Small, finely divided leaves form compact basal clumps. Tight rose lilac flower heads bloom atop four- to six-inch stems from spring through much of summer.
S. ochroleuca (zones 4 to 10) is a biennial or short-lived perennial valued for its one-inch creamy yellow globe flowers topping stems one to two feet tall. This wispy, fine-textured plant with deeply cut gray-green leaves combines nicely with blue-flowering plants, such as Russian sage (Perovskia).
Photography by Suzanne DeJohn/National Gardening Association